1. Field of the Invention
The present invention relates to an apparatus for etching and depositing a wafer or a glass using a plasma source, more particularly, to a plasma generation apparatus generating plasma using an induction electric field induced a time-varying magnetic field of a toroidal core.
2. Description of the Related Art
Generally, the plasma generation apparatus using the plasma source includes a plasma enhanced chemical vapor deposition (PECVD) apparatus for a thin film deposition, a reactive ion etching (RIE) apparatus etching a deposited thin film, sputter and ashing or the like.
In addition, the plasma generation apparatus is classified with a capacitive coupled plasma (CCP) apparatus and an inductive coupled plasma (ICP) apparatus in accordance with an applying type of a radio frequency (RF) power. At this time, the former generates plasma using a RF electric field vertically formed between electrodes by applying the RF power to planar electrodes facing each other, and the latter changes a source material into plasma using the induction electric field induced by a RF antenna.
Among them, the CCP type is more utilized than the ICP type. However, since ion energy of the CCP type is relatively high, defect possibility thereof is high regarding parts of a substrate or an inner of the apparatus due to an ion bombardment. Further, there is a problem not capable of using it in a low-pressure region less than a few mTorr as well as a difficulty that a line width or a selection ratio should be controlled.
Whereas the ICP type is effectively able to generate plasma in the low-pressure region in comparison with the CCP type. Further, the ICP type has an advantage capable of obtaining plasma having a much higher density than the CCP type. In addition, in the ICP type, the RF power is independently applied to the substrate different from the CCP type that the substrate is loaded on a susceptor functioning as an electrode. Accordingly, there is an advantage that the ion energy entered the substrate can be independently controlled.
FIG. 1 is a schematic cross-sectional view showing an ICP type plasma generation apparatus according to the related art.
As shown in FIG. 1, an ICP type plasma generation apparatus includes a chamber 11 having a chamber lid 11a and defining an airtight reaction region (not shown), a susceptor 12 in the chamber 11 and having a substrate “s,” a shower head 13 spraying a source material on a top surface of the susceptor 12, and a gas intake pipe 14 flowing the source material in the shower head 13.
Further, a RF antenna 15 supplying a RF power to the chamber 11 is disposed over the chamber lid 11a in order to change the source material into plasma. A RF power supply 17 is connected to the RF antenna 15.
A matching circuit 16 between the RF antenna 15 and the RF power supply 17 plays a role of matching load impedance and source impedance in order to apply a maximum power to the RF antenna 15.
At this time, when the RF power supply 17 is applied to the RF antenna 15, a time-varying magnetic field having a vertical direction occurs and an electric field is induced by the time-varying magnetic field in the chamber 11, wherein an accelerated electron collides with an electrically neutral ionized gas by the induction electric field. Therefore, a radical having a strong oxidation power is generated and the electron and the radical are changed into a mixture gas of a plasma state, so the radical is entered the substrate “s” and a process such as depositing and etching or the like is performed.
At this time, a different bias power (not shown) from the RF power supply 17 may be applied to the susceptor 12 in order to control an incident energy of the radical entered the substrate “s.”
Meanwhile, the susceptor 12 further includes a heater (not shown) therein for pre-heating the substrate “s” and an exhaust 18 under the chamber 11 exhausts a residual gas, for example, through a vacuum pump.
Hereinafter, FIG. 2 is a schematic cross-sectional view showing a coil type antenna according to the related art.
As shown in FIG. 2, a RF antenna 15 consists of a plurality of antenna coils 15a, 15b and 15c, wherein each of the antenna coils 15a, 15b and 15c is disposed over the chamber lid 11a and is connected to the RF power supply 17 via a matching circuit 16 by a RF cable 19.
Accordingly, when the RF power supply 17 is applied to the chamber 11, the time-varying magnetic field, which is orthogonal in each of the antenna coils 15a, 15b and 15c is generated and an electric field is induced in surrounding of the time-varying magnetic field.
However, among the induction electric field generated by the time-varying magnetic field, an induction electric field, which is suffered a loss, exists in a top portion of the chamber 11 besides the induction electric field utilized for generating plasma in the chamber 11. Further, it becomes had a structure that a leakage flux is generated a lot without a specific magnetic field shielding means. Accordingly, a high voltage RF power should be supplied to the chamber 11 to obtain a predetermined induction electric field for plasma generation and maintenance, as a result, a pollution source may occur in an inner wall of the chamber due to thermalization of the sputtering and parts by the high energy ion, and a loss of the RF power is undesirably increased.
To solve the problems, a method forming an induction electric field using a toroidal antenna 20 is suggested as shown in FIG. 3.
FIG. 3 is a schematic cross-sectional view showing a toroidal antenna according to the related art.
As shown in FIG. 3, a RF power is applied to the chamber 110 (of FIG. 1) by rolling a induction coil 11 surround of the toroid antenna 20 of a ferromagnetic such as a ferrite, most of flux of a time-varying magnetic field generated by the RF current flowing the induction coil 22 are induced along an inside of the toroid antenna 20. Therefore, much bigger flux density can be obtained than that of the related art using the coil type RF antenna 15. Accordingly, since the electric field intensity, which is induced in an opening portion 21 of the toroid antenna 20 can be significantly increased, finally, dissociation and ionization rate of the source material can be increased and a high-density plasma can be easily obtained.
That is, the present invention relates to the plasma generation apparatus generating plasma using the toroidal antenna 20, more particularly, the plasma generation apparatus according to the present invention is suggested so as to easily generate a high-density plasma under a low temperature and a low pressure in order to be applied to a high-integrated circuit pattern.
Recently, necessity regarding plasma for low temperature deposition is gradually increased centering around a manufacturing process such as a low temperature polysilicon (LTPS), an electron luminescence (EL) and a carbon nano tube (CNT) or the like. However, the plasma for the low temperature deposition demanded in this process, should have a plasma density more than about 2×1011/cm3 and an electron energy more than about 4 eV. Generally, the more the electron energy is high, the more a film quality is good.
Further, the more a process pressure is low, the more the film quality is good. Therefore, if possible, the plasma should be effectively burned and maintained under the process pressure less than about 5 mTorr. In addition, properly, the ion energy and the plasma electric potential should be low to prevent a substrate defect due to the ion bombardment.
For example, although the LTPS process according to the related art is performed a crystallization method such that crystallization of polysilicon without rise of the substrate temperature by a laser irradiation after depositing an amorphous silicon using a CCP type, there is an advantage capable of directly depositing the polysilicon on the substrate without the crystallization process upon using the plasma for the low temperature deposition.
Further, in case of an organic electro luminescent device such that an anode, a hole transport layer, a organic luminescent layer, an electron transport layer and a cathode are sequentially formed therein, wherein the hole transport layer, the organic luminescent layer, and the electron transport layer are generally made of an organic material. Here, since the organic material consists of monomer material, it is weak against moisture or a high energy. Accordingly, to solve the problem, although a process including filling a raw material in a melting pot, vaporizing the raw material and depositing the vaporized raw material on the substrate is suggested, but it is difficult that this process is applied to a large size substrate and a deposition speed is also slow.
Recently, the plasma generation apparatus using the toroidal antenna is suggested as an external model that the toroidal antenna is disposed on a plasma generation chamber additionally formed on the chamber and an internal type that the toroidal antenna is completely formed within the chamber without being exposed outside the chamber. Among them, in the external type plasma generation apparatus, since the plasma generation chamber is quite spaced apart from the main chamber, it is difficult that a high plasma density at a position corresponding to the substrate. In addition, since an eddy current occurs in a sidewall of the plasma generation chamber covering the external toroidal antenna and the induction electric field has a high rate defected by the sidewall of the plasma generation chamber, it is inevitable that energy transmission efficiency is low. Consequently, there is a disadvantage considering plasma burning and maintenance.
Meanwhile, in the internal type toroidal antenna, since an induction coil rolling the toroidal antenna is disposed with the chamber as well as the toroidal antenna, plasma impedance effects impedance of the induction coil connected to the RF power. As a result, matching condition of the RF power becomes unstable and a vacuum seal should be demanded to protect the induction coil or the RF power supply line from plasma. Particularly, when an exothermic temperature of the toroidal antenna is more than a Curie temperature, a ferromagnetic substance is changed into a paramagnetic substance. Therefore, the time-varying magnetic field does not occur in the chamber.
In addition, since magnetic permeability is changed or power loss is increased due to exothermal, it is important to appropriately cool the toroidal antenna. However, since the toroidal antenna is disposed within the chamber in case of the internal type, it is not easy to cool the toroidal antenna.